[CCF] FW: [CQ-Contest] Electric Fence QRN

jukka.klemola at nokia.com jukka.klemola at nokia.com
Thu May 8 14:34:24 EDT 2003

> -----Original Message-----
> From: ext Duane Grotophorst [mailto:n9dg at yahoo.com]
> Sent: 08 May, 2003 07:44
> To: cq-contest at contesting.com
> Subject: re: [CQ-Contest] Electric Fence QRN
> Having been both in farming and ham radio at the same
> some years ago I can attest that electric fences can
> be electrically quiet. When I was still on the farm we
> had miles of the stuff, some of it within 50 ft of my
> antennas, I had very little trouble with noise from
> it. My experience was that it is not the weeds growing
> into the fence and arching that generate the noise,
> including the "weed" burner type of fence charger. It
> is almost always instead a poor connection between
> fence segments, or between the fence charger and its
> ground system/rod.
> Think about a 3-6 KV (@ a few ma) circuit (being
> pulsed for .1 - .8 second durations) coupling to a
> high impedance antenna (the 1000's of feet of fence)
> through a spark gap (the poor connection). That is
> essentially a spark gap transmitter!!! However in the
> case of the weed growing into the fence it would be an
> arc through a relatively low impedance to ground.
> Since the weed stem is resistive and is also a short
> distance to ground it would not generate much, if any
> radio noise, even though the arching was very audible
> when you'd walk by it.
> When I was building electric fence I always used a
> "linemans" splice to connect different wire segments
> using minimum of 8 - 10 turns when joining sections.
> For areas that needed a gateway I always made sure
> that the wire that made up the gate would be pulled
> quite tight when connected to its hook. The bottom
> line that it came down to was making sure that all
> electrical connections were mechanically solid and
> proper. A sloppy job of making the connections didn't
> really hurt the fence's performance all that much for
> keeping the critters in there proper places, but it
> did make a big difference for RFI issues.
> Duane
> N9DG
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